Maturation of the neuromuscular junction in masseters of human fetus.

OBJECTIVES The aim of the present investigation is to examine if the histological maturation of the neuromuscular junction in the masseters of human fetuses has already begun by the 12-th week of gestation or not. MATERIAL AND METHODS Twenty-four masseter muscles from 14 human fetuses at gestational age 12 weeks were divided into two groups. In the first group, muscle sections were stained with Bielschowsky and Holzer stains for examination of neurofibrils and glial cells respectively. In the second group, rhodamine and fluorescein conjugated alpha-bungarotoxin were used to detect nicotinic receptors and anti-GAD for neuronal terminals. RESULTS It was observed the presence of one axon for each end-plate and glial cells spread over a branched axon. The nicotinic receptors clustered in the neuromuscular junction, neuronal terminals and large oval nucleus were detected. CONCLUSIONS These observations suggest that the maturation of the neuromuscular junctions of the masseter muscles in the human fetuses has already begun at the 12-th week of gestation.